The cathedral's bell tower is the world's tallest Eastern Orthodox bell tower. Since the belfry is not standalone, but an integral part of the main building, the cathedral is sometimes considered the highest Eastern Orthodox Church in the world. 1735 Tsar Bell The Tsar Bell, also known as the Tsarsky Kolokol or Royal Bell, is a huge bell on display on the grounds of the Moscow Kremlin. The bell was commissioned by Empress Anna, niece of Peter the Great. Currently it is the largest and heaviest bell in the world, weighing 216 tons, with a height of 6.14 m (20.1 ft) and diameter of 6.6 m (21.6 ft). It was founded from bronze by masters Ivan Motorin and his son Mikhail in 1733–1735. The bell, however, was never rung because of a fire in 1737, when a huge slab (11.5 tons) cracked off while it was still in the casting pit. In 1836, the bell was placed on a stone pedestal next to the Ivan the Great Bell Tower. For a time, the bell served as a chapel, with the broken area forming the door. According to the legend, on Judgement Day the Tsar Bell will be miraculously repaired and lifted up to heaven, where it will ring the blagovest (call to prayer). 1739 Ice palace 1740s 1741 Quick-firing gun by Andrey Nartov 1750s 1754 Coaxial rotor / Model helicopter by Mikhail Lomonosov 1756 Law of Mass Conservation by Mikhail Lomonosov 1757 Licorne (Russian field gun) by M.W. Danilov and S.A. Martynov 1760s 1761 Atmosphere of Venus Mikhail Lomonosov was the first person to hypothesize the existence of an atmosphere on Venus based on his observation of the transit of Venus of 1761 in a small observatory near his house in Petersburg. 1762 Off-axis reflecting telescope by Mikhail Lomonosov 1770s 1770 Amber Room The Amber Room in the Catherine Palace of Tsarskoye Selo near Saint Petersburg is a complete chamber decoration of amber panels backed with gold leaf and mirrors. It was dubbed the Eighth Wonder of the World due to its singular beauty and the large quantity of a rare material (amber is rather hard to carve). Due to its unique history it was also called the World's Greatest Lost Treasure. Several generations of German and Russian craftsmen worked on this masterpiece, prompted by several generations of monarchs. Construction began in 1701 to 1709 in Prussia. In 1716 the